LM675 Power Operational Amplifier

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LM675 www.ti.com SNOSBP3E – MAY 1999 – REVISED MARCH 2013 LM675 Power Operational Amplifier Check for Samples: LM675 1FEATURES Connection Diagram 23A Current Capability A VO Typically 90 dB 5.5 MHz Gain Bandwidth Product 8 V/μs Slew Rate Wide Power Bandwidth 70 kHz 1 mV Typical Offset Voltage *The tab is internally connected to pin 3 Short Circuit Protection (V EE ) Thermal Protection with Parole Circuit (100% Figure 1. Front View Tested) TO-220 Power Package (NDH) See Package Number NDH0005D 16V–60V Supply Range Wide Common Mode Range Internal Output Protection Diodes Typical Applications 90 dB Ripple Rejection Plastic Power Package TO-220 APPLICATIONS High Performance Power Op Amp Bridge Amplifiers Motor Speed Controls Servo Amplifiers Instrument Systems DESCRIPTION The LM675 is a monolithic power operational amplifier featuring wide bandwidth and low input offset voltage, making it equally suitable for AC and DC applications. The LM675 is capable of delivering output currents in excess of 3 amps, operating at supply voltages of up to 60V. The device overload protection consists of both internal current limiting and thermal shutdown. Figure 2. Non-Inverting Amplifier The amplifier is also internally compensated for gains of 10 or greater. 1 Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet. 2All trademarks are the property of their respective owners. PRODUCTION DATA information is current as of publication date. Copyright © 1999–2013, Texas Instruments Incorporated Products conform to specifications per the terms of the Texas Instruments standard warranty. Production processing does not necessarily include testing of all parameters.

Transcript of LM675 Power Operational Amplifier

Page 1: LM675 Power Operational Amplifier

LM675

www.ti.com SNOSBP3E –MAY 1999–REVISED MARCH 2013

LM675 Power Operational AmplifierCheck for Samples: LM675

1FEATURESConnection Diagram

2• 3A Current Capability• AVO Typically 90 dB• 5.5 MHz Gain Bandwidth Product• 8 V/μs Slew Rate• Wide Power Bandwidth 70 kHz• 1 mV Typical Offset Voltage

*The tab is internally connected to pin 3• Short Circuit Protection (−VEE)

• Thermal Protection with Parole Circuit (100% Figure 1. Front ViewTested) TO-220 Power Package (NDH)

See Package Number NDH0005D• 16V–60V Supply Range• Wide Common Mode Range• Internal Output Protection Diodes Typical Applications• 90 dB Ripple Rejection• Plastic Power Package TO-220

APPLICATIONS• High Performance Power Op Amp• Bridge Amplifiers• Motor Speed Controls• Servo Amplifiers• Instrument Systems

DESCRIPTIONThe LM675 is a monolithic power operationalamplifier featuring wide bandwidth and low inputoffset voltage, making it equally suitable for AC andDC applications.

The LM675 is capable of delivering output currents inexcess of 3 amps, operating at supply voltages of upto 60V. The device overload protection consists ofboth internal current limiting and thermal shutdown. Figure 2. Non-Inverting AmplifierThe amplifier is also internally compensated for gainsof 10 or greater.

1

Please be aware that an important notice concerning availability, standard warranty, and use in critical applications ofTexas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.

2All trademarks are the property of their respective owners.

PRODUCTION DATA information is current as of publication date. Copyright © 1999–2013, Texas Instruments IncorporatedProducts conform to specifications per the terms of the TexasInstruments standard warranty. Production processing does notnecessarily include testing of all parameters.

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LM675

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These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foamduring storage or handling to prevent electrostatic damage to the MOS gates.

ABSOLUTE MAXIMUM RATINGS (1) (2)

Supply Voltage ±30V

Input Voltage −VEE to VCC

Operating Temperature 0°C to +70°C

Storage Temperature −65°C to +150°C

Junction Temperature 150°C

Power Dissipation (3) 30W

Lead Temperature(Soldering, 10 seconds) 260°C

ESD rating to be determined.

(1) Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions forwhich the device is functional, but do not ensure specific performance limits. Electrical Characteristics state DC and AC electricalspecifications under particular test conditions which ensure specific performance limits. This assumes that the device is within theOperating Ratings. Specifications are not ensured for parameters where no limit is given, however, the typical value is a good indicationof device performance.

(2) If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/Distributors for availability andspecifications.

(3) Assumes TA equal to 70°C. For operation at higher tab temperatures, the LM675 must be derated based on a maximum junctiontemperature of 150°C.

ELECTRICAL CHARACTERISTICSVS=±25V, TA=25°C unless otherwise specified.

Parameter Conditions Typical Tested Limit Units

Supply Current POUT = 0W 18 50 (max) mA

Input Offset Voltage VCM = 0V 1 10 (max) mV

Input Bias Current VCM = 0V 0.2 2 (max) μA

Input Offset Current VCM = 0V 50 500 (max) nA

Open Loop Gain RL = ∞Ω 90 70 (min) dB

PSRR ΔVS = ±5V 90 70 (min) dB

CMRR VIN = ±20V 90 70 (min) dB

Output Voltage Swing RL = 8Ω ±21 ±18 (min) V

Offset Voltage Drift Versus Temperature RS < 100 kΩ 25 μV/°C

Offset Voltage Drift Versus Output Power 25 μV/W

Output Power THD = 1%, fO = 1 kHz, RL = 8Ω 25 20 W

Gain Bandwidth Product fO = 20 kHz, AVCL = 1000 5.5 MHz

Max Slew Rate 8 V/μs

Input Common Mode Range ±22 ±20 (min) V

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TYPICAL APPLICATIONS

VS = ±8V → ±30V

Figure 3. Generating a Split Supply From a Single Supply

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TYPICAL PERFORMANCE CHARACTERISTICS

THD vs Power Output Input Common Mode Range vs Supply Voltage

Figure 4. Figure 5.

Supply Current vs Supply Voltage PSRR vs Frequency

Figure 6. Figure 7.

Device Dissipation vs Ambient Temperature† Current Limit vs Output Voltage*

†θ INTERFACE = 1° C/W *VS = ±25VSee APPLICATION HINTS.

Figure 8. Figure 9.

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TYPICAL PERFORMANCE CHARACTERISTICS (continued)IB vs Supply Voltage Output Voltage Swing vs Supply Voltage

Figure 10. Figure 11.

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SCHEMATIC DIAGRAM

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LM675

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APPLICATION HINTS

STABILITY

The LM675 is designed to be stable when operated at a closed-loop gain of 10 or greater, but, as with any otherhigh-current amplifier, the LM675 can be made to oscillate under certain conditions. These usually involveprinted circuit board layout or output/input coupling.

When designing a printed circuit board layout, it is important to return the load ground, the output compensationground, and the low level (feedback and input) grounds to the circuit board ground point through separate paths.Otherwise, large currents flowing along a ground conductor will generate voltages on the conductor which caneffectively act as signals at the input, resulting in high frequency oscillation or excessive distortion. It is advisableto keep the output compensation components and the 0.1 μF supply decoupling capacitors as close as possibleto the LM675 to reduce the effects of PCB trace resistance and inductance. For the same reason, the groundreturn paths for these components should be as short as possible.

Occasionally, current in the output leads (which function as antennas) can be coupled through the air to theamplifier input, resulting in high-frequency oscillation. This normally happens when the source impedance is highor the input leads are long. The problem can be eliminated by placing a small capacitor (on the order of 50 pF to500 pF) across the circuit input.

Most power amplifiers do not drive highly capacitive loads well, and the LM675 is no exception. If the output ofthe LM675 is connected directly to a capacitor with no series resistance, the square wave response will exhibitringing if the capacitance is greater than about 0.1 μF. The amplifier can typically drive load capacitances up to 2μF or so without oscillating, but this is not recommended. If highly capacitive loads are expected, a resistor (atleast 1Ω) should be placed in series with the output of the LM675. A method commonly employed to protectamplifiers from low impedances at high frequencies is to couple to the load through a 10Ω resistor in parallel witha 5 μH inductor.

CURRENT LIMIT AND SAFE OPERATING AREA (SOA) PROTECTION

A power amplifier's output transistors can be damaged by excessive applied voltage, current flow, or powerdissipation. The voltage applied to the amplifier is limited by the design of the external power supply, while themaximum current passed by the output devices is usually limited by internal circuitry to some fixed value. Short-term power dissipation is usually not limited in monolithic operational power amplifiers, and this can be a problemwhen driving reactive loads, which may draw large currents while high voltages appear on the output transistors.The LM675 not only limits current to around 4A, but also reduces the value of the limit current when an outputtransistor has a high voltage across it.

When driving nonlinear reactive loads such as motors or loudspeakers with built-in protection relays, there is apossibility that an amplifier output will be connected to a load whose terminal voltage may attempt to swingbeyond the power supply voltages applied to the amplifier. This can cause degradation of the output transistorsor catastrophic failure of the whole circuit. The standard protection for this type of failure mechanism is a pair ofdiodes connected between the output of the amplifier and the supply rails. These are part of the internal circuitryof the LM675, and needn't be added externally when standard reactive loads are driven.

THERMAL PROTECTION

The LM675 has a sophisticated thermal protection scheme to prevent long-term thermal stress to the device.When the temperature on the die reaches 170°C, the LM675 shuts down. It starts operating again when the dietemperature drops to about 145°C, but if the temperature again begins to rise, shutdown will occur at only 150°C.Therefore, the device is allowed to heat up to a relatively high temperature if the fault condition is temporary, buta sustained fault will limit the maximum die temperature to a lower value. This greatly reduces the stressesimposed on the IC by thermal cycling, which in turn improves its reliability under sustained fault conditions. Thiscircuitry is 100% tested without a heat sink.

Since the die temperature is directly dependent upon the heat sink, the heat sink should be chosen for thermalresistance low enough that thermal shutdown will not be reached during normal operaton. Using the best heatsink possible within the cost and space constraints of the system will improve the long-term reliability of anypower semiconductor.

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POWER DISSIPATION AND HEAT SINKING

The LM675 should always be operated with a heat sink, even though at idle worst case power dissipation will beonly 1.8W (30 mA × 60V) which corresponds to a rise in die temperature of 97°C above ambient assuming θjA =54°C/W for a TO-220 package. This in itself will not cause the thermal protection circuitry to shut down theamplifier when operating at room temperature, but a mere 0.9W of additional power dissipation will shut theamplifier down since TJ will then increase from 122°C (97°C + 25°C) to 170°C.

In order to determine the appropriate heat sink for a given application, the power dissipation of the LM675 in thatapplication must be known. When the load is resistive, the maximum average power that the IC will be requiredto dissipate is approximately:

where• VS is the total power supply voltage across the LM675• RL is the load resistance• PQ is the quiescent power dissipation of the amplifier

The above equation is only an approximation which assumes an “ideal” class B output stage and constant powerdissipation in all other parts of the circuit. As an example, if the LM675 is operated on a 50V power supply with aresistive load of 8Ω, it can develop up to 19W of internal power dissipation. If the die temperature is to remainbelow 150°C for ambient temperatures up to 70°C, the total junction-to-ambient thermal resistance must be lessthan

Using θJC = 2°C/W, the sum of the case-to-heat sink interface thermal resistance and the heat-sink-to-ambientthermal resistance must be less than 2.2°C/W. The case-to-heat-sink thermal resistance of the TO-220 packagevaries with the mounting method used. A metal-to-metal interface will be about 1°C/W if lubricated, and about1.2°C/W if dry. If a mica insulator is used, the thermal resistance will be about 1.6°C/W lubricated and 3.4°C/Wdry. For this example, we assume a lubricated mica insulator between the LM675 and the heat sink. The heatsink thermal resistance must then be less than

4.2°C/W − 2°C/W − 1.6°C/W = 0.6°C/W. (1)

This is a rather large heat sink and may not be practical in some applications. If a smaller heat sink is requiredfor reasons of size or cost, there are two alternatives. The maximum ambient operating temperature can berestricted to 50°C (122°F), resulting in a 1.6°C/W heat sink, or the heat sink can be isolated from the chassis sothe mica washer is not needed. This will change the required heat sink to a 1.2°C/W unit if the case-to-heat-sinkinterface is lubricated.

The thermal requirements can become more difficult when an amplifier is driving a reactive load. For a givenmagnitude of load impedance, a higher degree of reactance will cause a higher level of power dissipation withinthe amplifier. As a general rule, the power dissipation of an amplifier driving a 60° reactive load will be roughlythat of the same amplifier driving the resistive part of that load. For example, some reactive loads may at somefrequency have an impedance with a magnitude of 8Ω and a phase angle of 60°. The real part of this load willthen be 8Ω × cos 60° or 4Ω, and the amplifier power dissipation will roughly follow the curve of power dissipationwith a 4Ω load.

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Typical Applications

Figure 12. Non-Inverting Unity Gain Operation

Figure 13. Inverting Unity Gain Operation

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Figure 14. Servo Motor Control

IOUT = VIN × 2.5 amps/volti.e. IOUT = 1A when VIN = 400 mVTrim pot for max ROUT

Figure 15. High Current Source/Sink

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REVISION HISTORY

Changes from Revision D (March 2013) to Revision E Page

• Changed layout of National Data Sheet to TI format .......................................................................................................... 10

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PACKAGE OPTION ADDENDUM

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Addendum-Page 1

PACKAGING INFORMATION

Orderable Device Status(1)

Package Type PackageDrawing

Pins PackageQty

Eco Plan(2)

Lead/Ball Finish(6)

MSL Peak Temp(3)

Op Temp (°C) Device Marking(4/5)

Samples

LM675T ACTIVE TO-220 NDH 5 45 TBD Call TI Call TI 0 to 70 LM675T

LM675T/LF02 ACTIVE TO-220 NEB 5 45 Green (RoHS& no Sb/Br)

SN Level-1-NA-UNLIM 0 to 70 LM675T

LM675T/LF05 ACTIVE TO-220 NEB 5 45 Green (RoHS& no Sb/Br)

SN Level-1-NA-UNLIM 0 to 70 LM675T

LM675T/NOPB ACTIVE TO-220 NDH 5 45 Green (RoHS& no Sb/Br)

SN Level-1-NA-UNLIM 0 to 70 LM675T

(1) The marketing status values are defined as follows:ACTIVE: Product device recommended for new designs.LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.PREVIEW: Device has been announced but is not in production. Samples may or may not be available.OBSOLETE: TI has discontinued the production of the device.

(2) RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substancedo not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI mayreference these types of products as "Pb-Free".RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption.Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of <=1000ppm threshold. Antimony trioxide basedflame retardants must also meet the <=1000ppm threshold requirement.

(3) MSL, Peak Temp. - The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.

(4) There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device.

(5) Multiple Device Markings will be inside parentheses. Only one Device Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuationof the previous line and the two combined represent the entire Device Marking for that device.

(6) Lead/Ball Finish - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead/Ball Finish values may wrap to two lines if the finishvalue exceeds the maximum column width.

Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on informationprovided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and

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PACKAGE OPTION ADDENDUM

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Addendum-Page 2

continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals.TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release.

In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.

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MECHANICAL DATA

NDH0005D

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MECHANICAL DATA

NEB0005B

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IMPORTANT NOTICE AND DISCLAIMER

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